With the window closing fast for anyone wanting to escape, Hurricane Irma moved toward Florida with 200 km/h winds Saturday after battering Puerto Rico, the Dominican Republic and the northern coast of Cuba.

"You need to leave — not tonight, not in an hour, right now," Gov. Rick Scott warned residents in the evacuation zones ahead of the storm's predicted arrival on Sunday morning.

"This is your last chance to make a good decision."

For days, the forecast had made it look as if the Miami metropolitan area of six million people could get hit head-on with the catastrophic and long-dreaded Big One, but the hurricane's track has shifted.

The U.S. National Hurricane Center said late Saturday Irma's projected path is continuing to shift to the west, which should keep its eye just off Florida's west coast on a track to hit St. Petersburg, not Miami or even Tampa.

The hurricane's leading edge was already lashing the Florida Keys with hurricane force winds. If the centre of the storm keeps moving over warm Gulf of Mexico water, it may regain more strength before making landfall again.

The storm currently has top sustained winds of 193 km/h and is moving northward at about 10 km/h.

A man walks down a deserted highway in Miami as Hurricane Irma approaches on Saturday. (Roberto Koltun/Miami Herald via AP)

Nearly seven million people across the state were under evacuation orders. More than 75,000 people in Florida were seeking shelter Saturday in schools, community centres and churches.

The westward swing in the hurricane's projected path overnight caught many on Florida's Gulf coast off-guard. By late morning, few businesses in St. Petersburg had even put plywood or hurricane shutters on their windows, and some locals groused about the change in the forecast.

"For five days, we were told it was going to be on the east coast, and then 24 hours before it hits, we're now told it's coming up the west coast," said Jeff Beerbohm, a 52-year-old entrepreneur in St. Petersburg. "As usual, the weather man ... I don't know why they're paid."

Now, Hurricane Jose is moving in a westerly direction and is expected to pass close to the islands of Saint Martin and Saint Bart's later Saturday. In the Atlantic, Jose was a Category 4 hurricane early Saturday, about 300 kilometres east-southeast of the Northern Leeward Islands.

A resident of Barbuda, heavily damaged by Irma, told CBC News the island will be spared another hit because Jose has already passed the island.

Late Friday, Irma had Category 5 strength with winds of 260 km/h as it made landfall near the popular resort town of Cayo Coco in Cuba's Ciego de Avila province. The storm then weakened to Category 4 strength early Saturday.

"The meteorological equipment used by the Cuban government to determine the wind speed was broken by this powerful storm," CNN reporter Patrick Oppmann told CBC News, reporting from nearby Caibarien.

Long lineups at shelters

In one of the biggest evacuations ever ordered in the U.S., about 6.4 million people in Florida — more than one-quarter of the state's population — were warned to leave. Gas shortages and gridlock plagued the evacuations. Parts of interstates 75 and 95 north were bumper-to-bumper.

Some 75,000 people crowded more than 400 shelters across Florida. At Germain Arena not far from Fort Myers, on Florida's southwestern corner, thousands waited in a snaking line for hours to gain a spot in the hockey venue-turned-shelter.

Florida Power and Light said on its website more than 170,000 homes and businesses have lost power. The company said it expects millions of people to lose power, with some areas experiences prolonged outages.

People wait outside the Germain Arena to take shelter from Hurricane Irma in Estero, Florida, just south of Fort Myers. (Bryan Woolston/Reuters)

Among those weathering the storm is Canadian Christopher McLaughlin, a veterinarian at Coral Springs Animal Hospital, which is taking in pets from evacuees who can't bring their animals to shelters.

"We have dogs and cats tucked in everywhere here, well over 300 animals in all the different hallways and bathrooms, essentially everywhere," he told CBC News Network Saturday.

"We are packed but are doing OK."

He said Irma has already been "one of the more trying experiences" of his life.

"We just bought a brand-new house last week, and didn't have any hurricane protection. We're not at all ready like we should have been, unfortunately," he said.

Hurricane Irma's expected path shifted Saturday so that it looked likely to hit southwest Florida, rather than the east coast, as originally predicted. The change caught many on Florida's Gulf coast off-guard. (CBC)

Forecasters warned of storm surge as high as 4.5 metres along a swath of southwest Florida and beyond.

"This is going to sneak up on people," said Jamie Rhome, head of the hurricane centre's storm surge unit.